It's not often that a company like Porsche is the underdog. But as they gear up for the 24 Hours of Le Mans this weekend, that's exactly what they are. Returning to the race for the first time since the late 1990s, they're up against far more established teams, most notably corporate cousin Audi. How can they possibly expect to win?

The 24 Hours Of Le Mans starts this Saturday, and promises to be one hell of a race. There's…
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With technology, that's how. They're calling their 919 Hybrid "the most complex Porsche race car ever," and considering the company's race car output over the decades, that's no small statement.

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Porsche explains that they're at something of a disadvantage compared to more established teams. They don't have the experience or data from previous races to draw on, outside the GT category the 911 is running in, and they used their own engineers to develop the LMP1-H car rather than rely on outside companies.

But Porsche says this also gave them a lot of freedom on how to create their hybrid prototype racer. As with every Le Mans race, efficiency is the key here, and the way Porsche has gone about that is pretty fascinating.

As you've probably heard, the 919 is powered by a 2.0-liter direct injection, turbocharged, gasoline-powered V4 with 500 horsepower mated to a hybrid electric drive system with more than 250 horsepower.

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Porsche says they decided to drop the kinetic energy recovery system on the rear axle in favor of one on the front axle. As the weight of the car shifts to the front during braking, they believe they can exploit kinetic energy on a greater level.

But that's not really the interesting part — thermodynamic energy recuperation is. Because the car is turbocharged, it gave Porsche a few options on how to increase efficiency.

Instead of a wastegate like on a normal turbo car, the engine has an extra turbine generator unit driven by exhaust gases. This turbine takes the exhaust and uses it to produce electrical energy. (The current turbocharged Formula One cars also turn heat and exhaust from the turbo into electric juice.)

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Porsche says this makes the 919 Hybrid "the only car in the field that recuperates energy not only when it brakes but also when it accelerates."

Porsche is running in the six megajoule (6MJ) hybrid class with the 919, which means the car can use exactly 1.67 kilowatt hours of energy per 13.629 km (8 mile) long lap at Le Mans. Under these rules, the gasoline engine is only allowed to consume 4.78 liters of fuel (about 1.25 gallons) per lap at Le Mans. The cars have to use 30 percent less fuel than last year.

But Porsche seems to have efficiency on their side. The company says that in 2013, the winning car covered 348 laps — with their system over the same distance, they believe the 919 can produce enough energy to run a 60 watt light bulb for 9,687 hours. That's unbelievable.

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Will the 919's innovative kinetic and thermodynamic energy recuperation systems be enough to take on the diesel-powered giant that is Audi, or will it end in failure? We'll find out this weekend.